1. Field of the Invention
The present invention relates to an object observation apparatus and, more particularly, to an apparatus and method of observing the integrated circuit pattern of a semiconductor wafer or the like using, e.g., an electron beam.
2. Related Background Art
With higher integration degrees of recent LSIs, the defect detection sensitivity required for samples such as a wafer and mask is increasing. For example, to detect defective portions on a wafer pattern 0.25 xcexcm in DRAM pattern size, a detection sensitivity of 0.1 xcexcm is required. In addition, demands have arisen for inspection apparatuses which satisfy both an increase in detection sensitivity and an increase in detection speed. To meet these requirements, surface inspection apparatuses using an electron beam have been developed.
A known example of an apparatus for scanning an electron beam on an object and observing secondary electrons from the object is a scanning electron microscope (SEM). A known example of an inspection apparatus for inspecting defects using an electrooptic system as a primary optical system is one disclosed in Japanese Patent Laid-Open No. 7-181297 (corresponding to U.S. Pat. No. 5,498,874). As disclosed in Japanese Patent Laid-Open No. 7-249393 (corresponding to U.S. Pat. No. 5,576,833), a pattern inspection apparatus is known which forms the sectional shape of a beam into a rectangular or elliptic shape through a rectangular cathode and quadrupole lens.
However, the conventional apparatuses are difficult to realize high-precision observation of an object using an electron beam.
It is, therefore, an object of the present invention to provide an observation apparatus and observation method capable of observing a clear image of an object to be observed at a high precision.
It is another object of the present invention to provide an object observation apparatus characterized by comprising a drivable stage on which a sample is placed, an irradiation optical system which is arranged to face the sample on the stage, and emits an electron beam as a primary beam, an electron detection device which is arranged to face the sample, has a detection surface on which at least one of a secondary electron, reflected electron, and back-scattering electron generated by the sample upon irradiation of the electron beam is projected as a secondary beam, and generates image information of the sample, a stage driving device which is adjacent to the stage to drive the stage, and a deflector arranged between the sample and the electron detection means to deflect the secondary beam, the electron detection device having a converter arranged on the detection surface to convert the secondary beam into light, an array image sensing unit which is adjacent to the converter, has pixels of a plurality of lines each including a plurality of pixels, sequentially transfers charges of pixels of each line generated upon reception of light of an optical image obtained via the converter to corresponding pixels of an adjacent line at a predetermined timing, adds, every transfer, charges generated upon reception of light after the transfer at the pixels which received the charges, and sequentially outputs charges added up to a line corresponding to an end, and a control unit connected to the array image sensing unit to output a transfer signal for sequentially transferring charges of pixels of each line to an adjacent line, and the control unit having a stage scanning mode in which the array image sensing unit is controlled in accordance with a variation in projection position of the secondary beam projected on the electron detection device that is generated by movement of the stage device, and a deflector operation mode in which the array image sensing unit is controlled in accordance with a variation in projection position of the secondary beam projected on the detection device that is generated by operation of the deflector.
It is still another object of the present invention to provide an object observation apparatus comprising an irradiation optical system which is arranged to face a sample, and irradiates the sample surface with an electron beam, an electron detection device which is arranged to face the sample, and detects as a secondary beam at least one of a secondary electron, reflected electron, and back-scattering electron generated by the sample upon irradiation of the electron beam, a deflector arranged between the irradiation optical system and electron detection device and the sample, irradiates the sample surface with the electron beam from the irradiation optical system, and guides a primary beam generated by the sample to the electron detection device, an objective electrooptic system arranged between the deflector and the sample, and a limiting member arranged at a focus position of the objective electrooptic system to limit the secondary beam amount, wherein the objective electrooptic system and limiting member constitute a telecentric electrooptic system.
It is still another object of the present invention to provide an object observation method of observing an object using an electron beam, characterized by comprising the irradiation step of irradiating the object on a stage with the electron beam, the conversion step of projecting a secondary beam from the irradiated object onto a fluorescent portion, and converting the secondary beam into light at the fluorescent portion, and the image sensing step of detecting image information of the light, converted at the fluorescent portion, with pixels of a plurality of lines each including a plurality of pixels, sequentially transferring charges generated in pixels of each line to corresponding pixels of an adjacent line at a predetermined timing, adding, every transfer, charges generated upon reception of light after the transfer at the pixels which received the charges, and sequentially outputting charges added up to a line corresponding to an end, the image sensing step having a stage scanning mode in which a projection position of the secondary beam from the object moving with movement of the stage is varied, and a deflector operation mode in which the projection position of the secondary beam from the object is varied by operating a deflector.
It is still another object of the present invention to provide an object observation apparatus characterized by comprising a drivable stage on which a sample is placed, an irradiation optical system which is arranged to face the sample on the stage, and emits an electron beam, an electron detection device which is arranged to face the sample, has a detection surface on which at least one of a secondary electron, reflected electron, and back-scattering electron generated by the sample upon irradiation of the electron beam is projected as a secondary beam, and generates image information of the sample, an electrooptic system arranged between the sample and the electron detection device to form the secondary beam into an image on the detection surface of the electron detection device, and a position detection device which is adjacent to the stage to detect a position of the stage, the electron detection device having a converter arranged on the detection surface to convert the secondary beam into light, an array image sensing unit which is adjacent to the converter, has pixels of a plurality of lines each including a plurality of pixels, sequentially transfers charges of pixels of each line generated upon reception of light of an optical image obtained via the converter to corresponding pixels of an adjacent line at a predetermined timing, adds, every transfer, charges generated upon reception of light after the transfer at the pixels which received the charges, and sequentially outputs charges added up to a line corresponding to an end, and a control unit connected to the array image sensing unit to output a transfer signal for sequentially transferring charges of pixels of each line to an adjacent line, the control unit controlling the array image sensing unit using a detection signal from the position detection device.